The electromagnetic lens and the deflection system in the well-known control circuits for electron beams in electron beam evaporators supplied with a direct acceleration voltage are connected to a DC source (adjustable DC amplifier). For stabilization of the electron beam, the currents across the electromagnetic lens and deflection coils are controlled according to the following formula: ##EQU1## where k is a constant, Ib is the current of the electron beam, Ub is the acceleration voltage.
There is a well-known circuit containing an acceleration voltage divider, the output of which, across a means for extracting root of four, is connected to one of the inputs of a divider unit. The output of a means for extracting a square root of the electron beam current is connected to the other input of that unit. The output of the divider unit is connected to the input of a control unit the output of which is connected to the focusing lens. See. USSR Author's Certificate No. 10 50 011 A, SU.
It is a disadvantage of the known circuits that they control electron beams supplied with direct acceleration voltage only, which need rectification and filtering of the acceleration high voltage which makes the equipment more expensive, reduces its reliability and reduces its efficiency. The known circuit works following the formula (I) which is the reason for increasing the number and complexity of the units. Furthermore, DC amplifiers are used in the known electron beam control units, and these amplifiers are plagued by their inherent zero drifts, fluctuations, complex operation, etc.
It is an object of this invention to provide a circuit for electron beam control in electron beam evaporators with alternating acceleration voltages, having a reduced number of high voltage components, improved reliability and efficiency factor, being simultaneously less expensive; for correcting the focus ratio depending on the electron beam length; for electron beam stabilization by reduced number of units and using AC amplifiers.